X-ray system.



H. C. SNOOK.

X-RAY SYSTEM.

APPLICATION FILED APR. 13. 1909. RENEWED NOV. 9.191s.- l @7 PatentedJuly 10,1917.

2 SHEETS-SHEET l- W mm 3 4" I SSHEET 2.

Patented July 10, 1917.

Mm m NQQ Q 5 W3 APPLICATION FILED APR-1'3, 1909- RENEWED NOV- 9. 1916.

mam? strength than air,

x-nnr SYSTEM.

1,233,137. Application filed April 13, 1909, Serial No. 489,551.

To all whom it may concern:

Be it known that LHoMan CLYDE SNOOK, a citizen of the United States,residing in the city of Philadelphia, county of Philadelphia, and Stateof Pennsylvania, have invented a certain new and useful Improvement inX-Ray Systems, of which the following is a specification.

My' invention relates to a system and apparatus for delivering highpotential unidirectional current to an X-ray tube or other translatingdevice, or to a consumption circuit.

My invention resides in a system and apparatus involving and carryingforward'the principles described and claimed in my Letters Patent of theUnited States No. 954,056 and N '0. 1,131,870. i

My invention resides in a system and ap paratus involving a switch forrectifying high potential alternating currents for general use, andparticularly for the excitation of X-ray tubes, whereby substantiallyall or any desired smaller part of each half current wave in a 'singlephase system or a large or other suitable fraction of each half wave ina poly'phase system is delivered to the X-ray tube or other translatingdevice or circuit, and all of the half waves delivered in the samedirection. And in my system and apparatus the high potential rectifyingswitch is of small dimensions considering the potentials involved andits relatively moving contacts are submerged in a. medium having fargreater dielectric such as oil, a compressed air or other gas, etc. 7

My invention resides in an X-ray system in which the resistance of theX-ray tube circuit is maintained substantially constant and is devoid ofresistance pulsations such as have been caused in prior systems by airgaps varying in length; and my invention resides in an X-ray system inwhich connection from the X-ray tube toJthe means delivering highpotential impulses is through a rectifying switch and a' path ofunvarying resistance, the resistance through and between the'cooperating rectifying switch con-, tacts being practically constant forall relative positions of those contacts.

My, system herein described is similar to the polyphase system describedin my aforesaid Patent'No. 1,131,870, in that the high potential energyof olyphase current is transmitted as uni-directional uninterrupt-Specification of Letters Yatent.

Patented July 10, 1917. Renewed November 9, 1916. Serial No. 130,476.

ed high potential energy to the consumption or work circuit. And in mypresentsystem the advantages as .to lar to those of the system of mysaid prior application, in that the digging or pitting of the target oranti-cathode, with a given mean energy, is reduced, fluctuation in X-raytubes are simivacuum is also reduced-and greater uniform ity of raysprocured.

In the system herein described, however, there is a further advantage,in that fluctuations in resistance in the consumption or work circuitare substantially suppressed, because in-the switching apparatus actualengagement takes place between the relatively moving contacts, air gapsbeing avoided, as above described.

I accordingly believe myself to be the first to deliver to a.work .orconsumption circuit uni-directional high tension current, that is,current at voltages higher than five thousand or ten thousand voltsupward to more than one without substantial fluctuation of resistance ofthe consumption circuit, particularly when the consumption circuitcontains a vacuum or X-ray tube, and when, the energy delivered to theis'either single or polyphase current, and when polyphase current,causing delivery of uninterrupted uni-directional current to theconsumption circuit.

My invention resides also in other fea-. tures hereinafter described andclaimed.

For an illustration ofsom'e of the forms my invention may take,reference is to be had to the accompanying drawings, in which: v hFigure 1 is a diagrammatic view illustrating the apparatus and circuitarrangements of my system involving a rectifying switch such as shown inFigs.- 3 and .4. a Fig. 2 is a diagrammatic view illustrating myapparatus" and system involving a modified form of rectifying switch,such, for 6X1 Fig. 4:

alternating curis a horizontal sectional view, partly in plan,-taken onthe'line 2- 2, Flg. 3, and

looking in'the' direction of the arrows.

Fig. 5 1s a fragmentary. view of a modihundred thousand volts,

switching. mechanism- 3 is a vertical elevational view, partly I highpotenmember of the prollO -- adjustable resistances {1, preferablynon-in- 7 ductive resistance 22.

ductive, to the pr1mariesp ,p and p of the -'threephase transformer Thaving the high potential secondaries 8 ,8 and 8 here shown 0 as Yconnected and having their common terminal connected tolearth 6 byconductor 5. The three'transformer secondaries have theirother'terminals connected through the high" frequency choke coils D withthe brushes .7, 8-, and 9 which bear respectively. upon. the three sliprings 10, 11, and 12 of the high potentialrectifying switch E such as.shown in Figs, 3 and 4. The slip ring 10 connects by conductor 13 withthe con-- ducting arcs 14; the slip ring 11 connects by conductor 15with the conducting arcs 16; and'the slip ring 12 connects by conductor17 with the conducting; arcs 18.

In .the arrangement shown, a pair of roller brushes 19, 19 is disposedsubstantially at right 'angles to a similar pair of brushes 20, 20*. Thedistance between the points of contact of the roller brushes of eachpair is substantiallfequal to the width of the in: sulation 21, betweenneighboring conducting -segments or arcs 14', 16, 18, and shouldpreferably be notgreaterithan the width of the; insulation 21. And it isdesirable that the width of the insulation 21 between con ducting arcsor segments should not begreater than the circumferential width orangular extent of the conducting ar'cs or segments themselves. And'theroller brushes of. each pair are not in direct electrical com-.munication'with each other. but are "conmated by a high inductive orhigh non-inserves to minimize current flow between the two-brushes towhich it'is connected during the timethat those brushes are in contactwithdifi'erent conducting arcs or segments.

And from points at substantially the middle,

of the high inductances or non-inductive resistances 22 extend theconductors 23 and 24 to the two terminals of an X-ray tube or- I othertranslating device" X, an ammeter'F;

"medium of slip-rings, and a .pair of col if desired, intervening in oneof these conductors as 24.

In the system just described stationary windings in which polyphase E.M. FLs. are, induced or developed are connected to ro-' tating contactsegments or arcs through the lectors cooperates with the contactsegments I sumption circuit.

The resistance 22 or arcs to take off unidirectional current.

' Here one mechanical'cycle of the rectifying "switch E corresponds withtwo electrical cycles. 1

The apparatus may also be arranged with connections from the stationarywindings to stationary contact arcs or segments the brushes-orcollectors then becoming the rotating members.

And, if four collectors be used instead of two as shown, and threeneighboring arcs connected to three slip rings, the cross con nectionsbetween the conducting arcs or segments need not be used with twoelectrical cycles to one mechanical cycle, opposing pairs of collectorsbeing in 'such case connected together.

The rotating element of the rectifying switch E is driven in synchronismwith'the current which it rectifies, and by preference by amechanicalconnection with the rotating member of the source orgenerator G whichdelivers the alternating current to the transformerT, which preferablyhas very small magnetic leakage.

The switch E rectifies-thecurrent in each of the three phases so thatthere are in effect overlapping half waves in the con- These overlappinghalf waves then cause -in the circuit of the tube X unidirectionalimpulses-of a frequency triple the frequency of one-half cycle suppliedby the transformer T. And this triple frequency current has a potentialor voltage which is higher than the voltage of any one of thesecondaries 8 ,8 or s.

- While the arcs or segments 14, 16 and 18 may be less than 60mechanical degrees or 120 electrical degrees in extent,. yet the periodof contact with each are or segment, because each pair of brushesconstitutes separate contacts connected through a high inductance orhigh resistance, is substantially equal to a time corresponding with 120electrical degrees- In' Fig. 3 is shown the inverted rotary R or agenerator G of the current delivered to the transformer T. Thisgenerator or converter is supported ,by the bracket 25 upon the plate ormember 26 preferably of insulating material, which is in turn su portedon any suitable device. or member 2 Extending through a bushing 28 inthe member 26 is the shaft 29 upon, which is secured theinsulatingmaterial 30, such as hard rubber. Upon the member 30' aremounted the slip rings 10, 11-, and 12 which are connected by conductors13, 15"and 17, as shown in Fig. 1, (and extending through the mass 30)with the conducting arcs or segments 14, 16 and 1'8, respectively,which, as before stated, are

separated by insulation 21,'Which may consist of blocks of mica or othersuitable maments and secured in the mass 30 of insulating material. Uponthe slip. rings 10, 11, and 12 bear the brushes, preferably rollerbrushes, 7, 8, and 9, as shown, such brushes being supported by 31depending from the plate or member 26 and connected at their bottom. bya yoke 32 having at its center a bearing 33 for the lower end of theshaft 29. This shaft is directly coupled to the shaft 34 of thegenerator or converter R, an insulating coupling 35 intervening.

Adapted tocontact the conducting arcs or segments 14, 16 and 18 are thepairs of roller contacts 19, 19"and 20,20 each pair being supported uponan insulating member 36 resiliently mounted by a leaf spring 37 upon thesupport 38 held in position upon the vertical insulating members 31;Springs 39 press inwardly upon the members 36 to cause the rollerbrushes to maintain physical contact with the conducting segments orarcs 14, 16 and 18 and their intervening insulation 21, the springs 39bearing at their outer ends agamst'the inner walls of the tank or casing40 supported by the plate or member 36 and containing oil to a level'above all of the slip rings, conducting arcs or segments, and theircooperating brushes or collectors.

- Or the chamber formed by the tank or inclosure 40 may be air or gastight and may contain any suitable gas or other material having agreater disruptive voltage than air, air or gas under pressure beingavailable when suitable.

By the arrangement shown the system disclosed in Fig. 1 may be used witha high potential rectifying switch occupying'a minimum of space orvolume and yet operating satisfactorily to rectify the alternatingcurrent of high potential, as, for example, from 50,000 to 150,000volts.

In Fig. 2, the primaries of the-- transformer T and the rotary converteror gen-' erator R or-G are not shown. The secondaries s 8 and s are thesame as shown in Fig. 1 and are connected through the high frequencyinductances D with roller or other brushes of a rectifying switch Hcomprising the three disks to, tv and 0.0 of insulating material capableof withstanding the high potentials involved, there being one of theseinsulating disks for each phase of the transformer secondary current.The transformer in this case again is preferably of a type having verysmall magnetic leakage. Set into the insulating disk w is a conductingare 41 which extends entirely through the disk w and has an exposed faceon each side of the disk. On one side of the disk, the front, forexample, are arranged the four roller brushes or other contactingdevices 42 all electrically connected together and to a terminal of thesecondary .9 On the other side of the disk, the rear, for extheinsulating members I both connected to ample, are the two pairs ofopposed roller brushes or similar contacting devices, one pair 43, 43electr'icallyconnected to the conductor 23, and a similar pair 44, 44disposed at right angles to the first pair and both electricallyconnected to the conductor 24, the conductors 23 and 24 being thtconsumption circuit including the X-ray tube X, or other suitabletranslating device, an ammeter F as shown being included in suchcircuit. The three disks w Q0 403 are all mechanically connected to anddriven by a shaft 29,

preferably mechanically connected to the converter or generator R or Gsuch as'shown in Figs. 1 and 3. p

The second disk 'w has a conducting are 45 .set in, but this arc is in adifferent angular positlon with respect to the driving shaft than theare 41 "of the disk w. And with disk w are associated four rollerbrushes or contacting. devices 46 on the front side all connectedtogether and to the terminal of the secondary 8 On the rear the opposingpair of similar contacting devices 47 are electrically connected to theconductor 23; while the pair 48v disposed at-right angles to the pair 47are also electrically connected to the conductor 24. And finally, inthe,case of disk 'w we have a third conducting are 49 set in andcooperating with the four roller or other contacting devices 50 on thefront side, all connected to a terminal of the secondary s and theopposed pair51 on the rear side connected to the conductor 23, and thesecond pair 52, at right angles, the conductor 24. As here shown each ofthe conducting arcs 41-, 45 and 49 has an angular or circumferential Iextent of substantially degrees corresponding with substantially 120electrical degrees, and each is shifted with respect to the othersubstantially 60 mechanical degrees or 120 electrical degrees.

When in operation, the shaft 29, as shown in Fig. 5, is rotated by theshaft of the converter or generator R or Gthus carrying the conductingarcs 41, 45 and 49 around in synchronism and thus closing circuitbetween opposed contacts or rollers and bringing the consumption circuit23 and 24 into communication with the secondaries of the transformer Tin a certain order of succession and at certain relative times'so thatto said consumption circuit there is delivered high potentialunidirectional current.

The switch H rect'ifies the current in each of the three phases so thatthere are, in effect, in the consumption circuit overlap-. ping halfwaves. These overlapping half waves then cause in the consumptioncircuit half waves of the three different phases, and

unidirectional impulses ofa frequency triple the frequency of one halfcycle supplied by the transformer T. And this triple frequency currenthas a potential or voltage which is higher than the voltage of any oneof'the secondaries s 8 or 8 f -The inserted conducting arcs, as 41, 45,and 49, may be slightly less than 60 mechani cal degrees or 120electrical degrees in extent,

but'they should be made substantially 60 mechanical degrees or 120electrical degrees in extent for a three phase system.

As seenfrom Fig. 6-, the hereinbefore described switching mechanisms.rectify the current of each phase, so that thereare the overlapping halfwaves a, I), 0, a, Z), and c, of which a, b and 0 represent the positivea, b and 0' represent the turned over negative half waves. The. sw tchrelations are such that each transformer secondary is in .circuit, foreach half wave for a time corresponding with the length 01. Thereresults a then in the circuit of the tube X a fluctuating current offrequency triple the frequency of a half cycle of one phase supplied bythe transformer T, this triple frequency current being represented bythe curve e in the upper part of Fig. 6. This curve is obtained byadding the prdinates of those parts of the curves below for-and duringsuch'periods as theditferent phases are. ac: tivelyin circuit ascontrolled by the switching mechanism. 'It will be noted that theminimum potential impressed upon the' ter- -minals of tube representedby the, distance f, is greater than the potential of any I 1 one of thesecondaries of the transformer T.

This curve shows that the tube X is constantly subjected to a potentialwhose mini mum is f which is always greater than the potentialdeliver-ed by any one phase of the transformer T, and thisminimumpotential f is sufficient to excite the tube X.

This minimum potential f'occurs at a moment or instant whenthe-secondary delivering the current wave a is in series with theother-two secondaries in parallel with-each other. Accordingly,theord-inate f is equal curve 0 plus the ordinate at the intersection tothe sum of the maximum ordinate of of the half waves a and 6 directlybelow the maximum of the curve c A maximum of understood that mysystemand rectifying apparatus are adaptable also to a single any numberemploy an air gap in the rectifying switch and do not employ aresistance which is synchronously varied. By my system substantially allof each half of the current waves, in a single phase system, or a largefraction in polyphase systems, ofboth signs, are impressed upon theconsumption circuit, and with small magnetic leakage in the transformerand by a mechanical connection between the rotating member of therectify-- ing switch and the rotatable member of the current producer,current in inverse direction in the consumption circuit is avoided, andin the case of an X-ray tube circuit, inverse discharge in the tube isprevented, thus resulting in the preventionof reduction of intensity ofexcitation of the tube and also in theprevention of shortening of lifeof the tube. -And from the fact that the resistance of thetube circuit,exclusive of the tube itself, is constant, a s attained by therectifying switch described, or from the additional fact of the lowmagnetic leakage of the transformer cooperating with theadvantages-produced by the rectifying switch, the

strength of the current through the 'X-ray I tube varies only 'with thevariation of the resistance of the tube itself.

While I utilize an alternating current, I' do not utilize only smallfractions or the crests of the current waves, though such may be used,but I preferably employ substantially all of each current wave, in asingle phase system, and do not suppress the current waves of one sign.And with a polyphase alternating current I do not utilize a smallfraction only of a current wave, though such may be used, but I employall the waves of bothsigns, and preferably utilize that fraction of eachhalf wave, symmetricallycn either side of thefmaXimum voltage, w ich isfound by dividingtwo by the number of phases in the alternating currentsupply.

'Thus, in a three phase system, I use twothirds of each half wave. And,in any case, I do not employ an air gap or a varyl g resistance, but bythe contacting devices shown and described, without any sparking, orvariation in resistance, I bring the X-ray tubeinto perfectly definiteelectrical connection with the wave source at a definite time.

I do not herein specifically claim subject matter of Fig. 2, but. claimthe same in my divisional application Serial Number 141,072,

'filed January 8, 1917'. \Vhat I claim is;

1. The combination with a source of high potentialalternating current,ofan X-ray tube, synchronous switching means for rectifying the currentdelivered to said tube and to said tube is reduced.

for connecting said tube with said source comprising'relatively movableing successively into engagement with each other, a resistanceperiodically bridging neighboring contacts,

tw'een-saidtube and said source of current,

whereby fluctuation 1n the energy delivered 2 The combination withpotential tube, of

a source of high alternating current, of an X-ray a synchronousrectifying switch comprising-relativelymovable brushes and contacts, abrush comprising separated contacts and a. resistance connecting saidsepa' rated contacts, said separated brush con.- tacts simultaneouslyperiodically engaging neighboring switch contacts, said resistance,

' brushes and contacts forming a continuous uninterrupted connection,between source of current and said 'X-ray tube, whereby fluctuation inthe energy delivered to said tube is reduced.

sumption circuithaving continuous uninter through said contacts, brushesand resistance. 4.--Thecomb1nation with a plurality of" tenti alrectifying switch windings as a H 3. The combmat'on with windingsdelivering high potential polyphase current, of

a consumption circuit, a synchronous recti- 1 fying switch interveningbetween said windings and said consumptionicircuit, said rectifyingswitch comprising relatively movable contacts and brushes coming intoengagement with each other, and means for introducing resistance betweensuccessivephase terminal of said consumption circuit is transferred fromone to another-of said phase windings, a terminal of said conruptedconnection with said windings windings delivering high potentialpolyphase current, an X-ray tube, and a high poconnected to saidwindings and to said X-ray 'tube and delivering to' said" X-ray tubeuninterruptedcurrent in one direction only, said switch havingrelatively movable contacts coming into engagement with each othermainta1ning continuous connection between said X- tial polyphasecurrent, of an X-ray a high potential rectifying switch passing ray tubeand said windings'through a path of unvarying resistance, whereby for agiven" mean of' energy delivered to said tube the maximum thereof andresultant destructive efiect upon said tube and variations in the raysare reduced.

5. The combination with a plurality of stationary windings deliveringhigh potentube, and

through .said X-ray tube in one direction only uninterruptedcurrent'from all the half waves of said polyphase current, said switchhaving relatively movable contacts coming into engagement with eachother maintaining continuous connection'between said X- contactscomwinding said resistance afiording continuous uninterrupted connectionbegaging sets of contacts, said .gular relations with ray tube and saidwindings through a path of unvarying resistance.

6. The combination with a stationary delivering high potentialalternating current, of a consumption circuit, a high potentialtranslating device in said circuit,

switching mechanism connecting said wind-- ing with said circuit,conducting arcs and brushes coming into engagement with said arcs, saidbrushes comprising contacts having diiferent angular relations with saidarcs,-aconductor of high resistance connecting said brushcontacts, and acircuit connection to said conductor.

7. The combination with a plurality of windings delivering highpotential polyphase current, of a high potential rectifying switchcomprising relatively moving and enan X-ray tube traversed always in thesame direction by energy delivered by said windings through saidcontacts, the resistance of the path through and between said sets ofcontacts remaining substantially constant for all relative positions ofsaid contacts.

8. The combination with stationary windings delivering high potentialpolyphase current, of an X-rav tube, a high potential switch interveningbetween 'said windings and said tube and comprising relatively rotatablecontacts and brushes'engaging each other, said brushes comprisingcontacts so spaced that one of said brush contacts makes connection withone of said first named contacts atfsubstantially the same instant another-of said brush contacts makes connecti'onwith the neXt succeedingof said first 10. A high potential rectifying switch comprisingconducting arcs or segments and cooperating brushes, the brushescomprising contacts engaging and having different ansaid arcs orsegments,.a symmetrically acting resistance connecting said contactstogether,

ances, and a source of polyphase high potential current deliveringenergy always in the same direction through said tube through saidrectifying switch,

an X-ray tube hav- 'ing its terminals connected to said resistsaid X-raytube con- .ti'nuously connected through said resistances, contacts andarcs or segments with said source through a path of unvarying 'resistance. 1

11. A system of X-ray tube excitation comprising a source of highpotential polyphase current, an X-ray tube, switching mechanismoperating in synchronism with said'current delivering uninterrupteduni-- directional current to said tube, said switching mechanismcomprising relatively movablev segments and brushes engaging each otherand maintaining continuous uninterrupted connection between said X-raytube and 'saidsour'ce of current through solid conductors, wherebyresistance pulsations in the circuit of said tube external to said tubeare prevented.

12. A system of X-ray tube excitation comprising a source of highpotential polyphase current, an X-ray tube, synchronous switchingmechanism delivering uni-directional uninterrupted current from saidsource to said tube, said switchin mechanism comprising relativelyrotating segvment's and brushes engaging each other, said saidrectifying switch comprising relatively lso movable contacts andbrushes, a brush com- -'prising separated contacts and a resistanceconnecting said separated contacts, said separated brush contactssimultaneously peri odically engaging neighboring switch contacts, saidresistance, brushes and contacts forming a continuous uninterruptedc0nnec tion between said source of current and said X-ray tube, wherebyfluctuation in the energy delivered'to said tube is reduced.

14. The combination with a generator of polyphase alternating current,of means for transforming said current to high potential polyphasecurrent, an X-ray ,tube, a high potential-polyphase rectifying switchwhose rotatable member is mechanically connected with the rotatingmember of said generator, said rectifying switch comprising relativelymovable brushes and contacts, a brush comprising separated contacts anda resistance.

connecting said separated contacts, said separated brush contactssimultaneously periodically engaging neighboring switch conwherebyfluctuation in the tacts, s'aid'resistance, brushes and contacts forminga continuous uninterrupted connection between said source of current andsaid X-ray tube, whereby fluctuation in the energy delivered to saidtube is reduced and "short circuitinglbetween different phases isprevented.

15. The combination with a generator of alternating current, of atransformer for stepping saidcurrent up to high potential, an X-raytube, a rectifying switch whose rotatable member is mechanicallyconnected with the rotating element of said generator, saidgeneratorproducing a plurality of electrical cycles for each revolution of therotatable member of said switch, said rectifying switch comprisingrelatively movable contacts and brushes, a brush comprising separatedcontacts and a resistance connecting said separated contacts, saidseparated brush contacts simultaneously periodically engagingneighboring switch contacts, said resistance, brushes and contactsforming a continuous uninterrupted connection between said source ofcurrent and said X-ray tube, energy delivered to said tube is reduced.

16. The combination with a generator of polyphase alternating current,of means for.

transforming said current to high-potential polyphase current, an X-raytube, a high potential polyphase rectifying switch whose rotatablemember is mechanically connected with the rotating member of saidgenerator,

said generator producing a plurality of electrical cycles for eachrevolution of'tlie rotatable member of said switch, said rec tifyingswitch comprising, relatively inovable brushes and contacts, a brushcomprising separated contacts and a resistance connecting said separatedcontacts, said separated brush contacts simultaneously periodicallyengaging neighboring switch contacts, said" resistance, brushes andcontacts forming a continuous uninterrupted connection between saidsource of current and said X-ray tube, whereby fluctuation in the energydelivered to said tube is reduced and short circuiting' betweendifferent phases is prevented.

17. The combination with a source of .high potential alternatingcurrent, of an X-ray tube, of a synchronous rectifying switch comprisingrelatively movable brushes and contacts, a brush comprising separatedcontacts and a resistance connecting said separated contacts, 'saidseparated brush contacts simultaneously periodically engagingneighboring switch contacts, and -a medium having greater dielectricstrcngth than that of air submerging said brush and switch contacts,said resistance, brushes and contacts forming a continuous uninterruptedconnection be-.

tween said source of current and said X-ray tube, whereby fluctuation inthe energy delivered to said tube is reduced.

18. The combination with a source of high potential fluctuating current,of an X-ray tube, means for connecting said tube with said source andfor rectifying the current delivered to said tube comprising relativelymovable contacts coming successively into engagement with each other, amass of material having greater dielectric strength than air in whichsaidmovable contacts are inclosed, and current restraining meanscocperating with said contacts affording continuous uninterruptednection between said tube and said source of current, wherebyfluctuation in the energy delivered to. said tube is reduced.

19. The combination with a source of high potential fluctuating current,of an X-ray tube,- synchronous switching means for rectifying thecurrent delivered to said tube andfor continuously connecting said tubewith said source comprising'relatively movable contacts comingsuccessively into engagement with each other, a mass of material havingair in which said contacts are submerged,

a resistance periodically bridging; neigh boring contacts, saidresistance affording f continuous uninterrupted connection between saidtube and said source of current, whereby fluctuation. in the energydelivered to said tube is reduced;

20. The combination with current, of a transformer netic leakagedelivering current at high higher dielectric strength than a source" ofhaving. small magpotential, an X-ray tube, means r'or connecting saidX-ray tube with said, transformer and for rectifying the currentdelivered thereby to said tube comprising relatively movable contactscoming success'ively into engagement with each other, and currentrestraining means cooperating with said contacts afiording continuousuninterrupted connection between said tube and said transformenwherebyfluctuation in the energy delivered to said tube is reduced.

21. The combination with a source of current, of a transformer havingsmall magnetic leakage delivering current at high potential, an X-raytube, means for connecting said X-ray tube with said transformer and forrectifying the current delivered thereby to saidgtube comprising rel--atively movable contacts coming successively into engagement with eachother,and

current restraining 'meansncocperating with said contacts afi'ordingcontinuous uninterrupted connection between said tube and saidtransformer, whereby fluctuation in r the energy delivered to said tubeis reduced,

said contacts being in engagement witheach other during a large part ofthe potential wave which causes passage of current therethrough.

In testimony whereof I have hereunto .aflixed mysignature in thepresence of the two subscribing witnesses.

, HOMER CLYDE SNOOK. WitnesSesz A. E, S'rrnnBocK,

E. T. MoGALL.

